added position field and copyWith constructor

lib/model/task.dart

@@ -12,6 +12,7 @@ class Task {
   final List<DateTime> alarms;
   final Location? location;
   final String url;
+  final int position;
 
   Task({
     required this.id,
@@ -25,5 +26,36 @@ class Task {
     this.alarms = const [],
     this.location,
     this.url = '',
+    required this.position,
   });
+
+  Task copyWith({
+    String? id,
+    String? title,
+    String? description,
+    DateTime? start,
+    DateTime? due,
+    bool? isCompleted,
+    String? category,
+    List<Task>? subtasks,
+    List<DateTime>? alarms,
+    Location? location,
+    String? url,
+    int? position,
+  }) {
+    return Task(
+      id: id ?? this.id,
+      title: title ?? this.title,
+      description: description ?? this.description,
+      start: start ?? this.start,
+      due: due ?? this.due,
+      isCompleted: isCompleted ?? this.isCompleted,
+      category: category ?? this.category,
+      subtasks: subtasks ?? this.subtasks,
+      alarms: alarms ?? this.alarms,
+      location: location ?? this.location,
+      url: url ?? this.url,
+      position: position ?? this.position,
+    );
+  }
 }